Pulsing Apparatus for Downhole Use

ABSTRACT

A pulsing apparatus for use in a conduit through which is flowing a liquid. The pulsing apparatus includes a housing in which is positioned a valve generally at the inlet of the housing, the valve controlling flow of fluid down a central passageway of the housing. There is also flow through an annulus of the housing formed in part by at least one rotor and one stator, the rotor rotating in response to fluid flow impinging on the vanes of the rotor. There is a second valve provided in the lower end of the housing through which flow can be intermittently interrupted to cause pressure pulses in the mud flow and hence in the conduit in which the pulsing apparatus is disposed, the second valve being operatively connected to the rotor.

FIELD OF THE INVENTION

The present invention relates to flow pulsing apparatus for use invarious applications, such as in down-hole operation in oil/gas wells,and in particular to a flow pulsing apparatus adapted to be connected ina drill string above a drill bit.

BACKGROUND OF THE INVENTION

In the drilling of oil and gas wells as well as other downholeactivities, it is common to use a downhole system which provides apercussive or hammer effect to the drill string to increase drillingrate and/or minimize sticking of the drill string in the borehole. Intypical drilling operations, a drilling fluid or mud is pumped from thesurface, through the drill string and exits through nozzles in the drillbit. The fluid flow from the nozzles assists in dislodging and cleaningcuttings from the bottom of the borehole as well as carrying thecuttings back to the surface.

Pulsing apparatuses for wellbore activities are well known asexemplified by U.S. Pat. Nos. 2,743,083; 2,780,438; 5,190,114; and6,279,670. In general, the flow pulses are achieved by periodicallyrestricting flow to produce pressure pulses. The pressure pulses aretranslated along the drill string causing the drill string to vibrate ina longitudinal direction, the net result being a percussive effect alongthe length of the drill string.

It is also common in addition to using the pulsing apparatus toincorporate a pressure-responsive tool in the drill string which expandsor retracts in response to the varying fluid pressure pulses created byoperation of the pulsing apparatus. This expansion/retraction motionprovides the desired percussive effect at the drill bit. Such anapparatus may be in the form of a shock sub or tool and, may be providedabove or below the pulsing apparatus or in certain cases can form partof a pulsing apparatus.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a downhole pulsingapparatus which can be used to impart periodic, longitudinal movement inthe drill string which can be transferred to the drill bit.

In another aspect, the present invention provides a pulsing apparatuswherein fluid flow through the apparatus can be modulated to control thefluid flow pattern through the pulsing apparatus.

In still a further aspect, the present invention provides a method ofimparting pressure pulses to a drill string wherein the frequency of thepulses can be controlled.

These and further features and advantages of the present invention willbecome apparent from the following detailed description, whereinreference is made to the figures in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically depicts a drill string including typical drillstring components drilling a deviated borehole.

FIG. 2A is an elevational view, partly in section, showing the first,upper end of one embodiment of the pulsing apparatus in accordance withthe present invention.

FIG. 2B is a view similar to FIG. 2A showing the second, lower end ofthe pulsing apparatus of FIG. 2A.

FIG. 3 is an enlarged view showing a portion of the pusling apparatusshown in FIG. 2A.

FIG. 4 is a cross-sectional view taken along the lines 4-4 of FIG. 3.

FIG. 5 is an enlarged view of the lower portion of the pulsing apparatusof FIG. 2B.

FIG. 6 is a cross-sectional view taken along the lines 6-6 of FIG. 5.

FIG. 7 is a cross-sectional view taken along the lines 7-7 of FIG. 5.

FIG. 8 is a plan view taken along the lines (8)-(8) of FIG. 5.

FIG. 9 is a partial elevational view, partly in section, showing theflow of fluid through a portion of the pulsing apparatus depicted inFIG. 8.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

While the invention will be described with respect to its use in a drillstring having a downhole motor, it is to be understood that it is not solimited. It can be used in other downhole operations, e.g., drillingwith tubulars, or in any other downhole operation involving a tubularstring through which a fluid is flowing. Thus the pulsing apparatus ofthe present invention can be used in work strings, fracking operations,etc.

Referring then to FIG. 1, there is shown an earth borehole 10 having avertical leg 12 and a horizontal leg 14. Extending from a derrick, mast,or the like 16 at the surface is a drill string shown generally as 18.String 18 has a series of bottomhole components comprising a drill bit20 driven by a downhole motor 22. String 18 also includes a measurementwhile drilling (MWD) module 24 which can include a steering tool andother sensors commonly employed to determine downhole parameters.Upstring of MWD module 24 is the pulsing apparatus 26 of the presentinvention, above which is directly positioned a shock sub 27. Thepositioning of the pulsing apparatus 26 and the shock sub 27 will varydepending on the nature of the borehole.

Turning now to FIGS. 2A and 2B, the pulsing apparatus 26 comprises ahousing shown generally as 28 having a first, upper end 28A and asecond, lower end 28B. Housing 28 is comprised of a series of threadedlyconnected subs, namely a first, upper sub 30, a second sub 32 and athird sub 34. Sub 30 is connected at its upper end to a drill stringelement 29 which can be a portion of the drill string, a sub, anothertool, etc. Lower sub 34 is also threadedly connected to a drill stringcomponent 36.

As used herein, and with respect to pulsing apparatus 26, the terms“upper,” “lower,” “up,” “down,” and similar terms are used with respectto the orientation of the apparatus in an earth borehole.

The pulsing apparatus 26 further includes a first valve assembly showngenerally as 40 and described more fully hereafter, valve assembly 40,in part, forming a first stator shown generally as 41 and also describedhereafter. Below valve assembly 40 is rotatably mounted a first rotorshown generally as 42 also described more fully hereafter. There is asecond stator shown generally as 44 positioned below rotor 42 and abovea second rotor shown generally as 46. There is a second valve assemblyshown generally as 50 which is positioned in housing 28 below secondrotor 46.

Referring now to FIGS. 2A, 2B, 3, and 4, the upper, first end of pulsingapparatus 26 is shown in greater detail. An annular, externally threadednipple 52 is threadedly received in an internally threaded bore 54 insub 30, sealing between sub 30 and nipple 52 being effected by an o-ringseal 56 received in an o-ring groove on the interior wall of sub 30. Asbest seen in FIG. 3, valve assembly 40 comprises a valve body 58, anannulus 61 being formed between valve body 58 and the inner wall ofnipple 52. A plurality of circumferentially spaced, fixed, angled vanes60 in annulus 61 connect valve body 58 to nipple 52. Valve body 58comprises an annular wall 64 and a frustoconical wall 66, frustoconicalwall 66 defining a circular opening forming an inlet 68 to valve body58. Mounted in valve body 58 is a concical shaped plug 70 connected to aspindle 74, spindle 74 being reciprocally mounted in a sleeve bearing76. There is a bushing 78 threadedly received in the lower end ofannular wall 64 of valve body 58. Bushing 78 comprises an outer, annularwall 78A, and an inner central concentric wall 78B, inner wall 78Bforming a bearing housing for bearing 76. An axially upwardly facing,annular shoulder 80 is formed on the upper end of inner wall 78B. Acompression spring 79 is connected to the underside of valve plug 70 andis in surrounding relationship to spindle 74. In the position shown inFIG. 2A, conical valve plug 70 substantially blocks valve inlet 68.However, in the position shown in FIG. 3, and under the influence offluid pressure acting against conical valve plug 70, spring 79 iscompressed increasing the flow area between conical valve plug 70 andvalve inlet 68. Accordingly, in the position shown in FIG. 2A, there isessentially no flow through valve 40, while in the position shown inFIG. 3 fluid flows through valve 40. To this end, bushing 78 defines avalve outlet 82.

As seen in FIG. 3, when sufficient fluid pressure caused by mud flowdown the drill string from a mud pump (not shown) at the surface isreached, valve 40 opens and there are essentially two flow paths, i.e. agenerally central flow path through valve 40 and a radially outer flowpath through annulus 61. It will be recognized by those skilled in theart that vanes 60 act as static guide vanes or nozzle vanes whichaccelerate and add swirl to the incoming fluid/drilling mud and directthe flow to the vanes of first rotor 42 as discussed hereafter.

There is a thrust bearing 90 positioned adjacent the lower end ofthreaded nipple 52.

Rotatably journaled in pulsing apparatus 26 is first rotor 42. Rotor 42comprises a tubular, central core portion 94 having a central passageway96. Passageway 96 communicates with a plurality of angled ports 106 fora purpose described hereafter. Rotor 42 also comprises a radiallyoutward annular sleeve portion 98 connected to and rotatable with coreportion 94, an annulus 100 being formed between core portion 94 andsleeve portion 98. As seen in FIG. 3, connecting core portion 94 andsleeve portion 98 are a plurality of circumferentially spaced, angledvanes 102. The swirling mud flow induced by stator vanes 60 impinges onvanes 102 resulting in rotational motion of first rotor 42. As well,flow of mud exiting ports 106 from passageway 96 also impinges on vanes102 resulting in rotation of first rotor 42. A radial sleeve bearing 89is positioned in counterbore 91 in surrounding relationship to sleeveportion 98.

Central core portion 94 of rotor 42, as best seen in FIG. 2A, includesan axially downwardly extending shaft portion 108 which projects towardsecond, lower end 28B of housing 28. Shaft portion 108 is received in anaxial bore 110 in the central core portion 111 of a second rotor 46 andis connected thereto by a pin 112 received in registering bores in shaftportion 108 and central core portion 111 of rotor 46, thereby rigidlyconnecting rotor 46 to rotor 42 for rotation therewith.

Sleeve portion 109 of rotor 46 is connected to core portion 111 by aplurality of circumferentially spaced vanes 114 positioned in an annulus121 between core portion 111 and sleeve portion 109. Fluid flow in theannulus 121 impinging on vanes 114 induces rotation of rotor 46 in asimilar manner as discussed above with respect to rotor 42.

The central core portion 111 of rotor 46 has an upper, axially facingsurface 118, while central portion 94 of rotor 42 has an annular,axially downwardly facing shoulder 130. Disposed between shoulder 130and the axially upwardly facing surface 118 of rotor 46 is a secondstator 44. Stator 44 carries upper and lower thrust bearing assemblies140 and 142 respectively and includes a central core portion 150 and aradially outwardly spaced sleeve portion 152 thereby forming an annulus154 therebetween. Interconnecting core portion 150 and sleeve portion154 are a plurality of circumferentially spaced, fixed, angled vanes156, vanes 156 acting in the same manner as described above with respectto vanes 60 of first stator 40 as a result of fluid flow in annulus 154.

As seen in FIG. 2B, there is a central passageway 180 formed by sleeveportion 109, passageway 180 being in open communication with a generallyradially outwardly angled flowport 181 having a funnel shaped mouth 182formed in a threaded fitting 183 which is threadedly received in athreaded interior socket of sleeve 109, fitting 183 rotating in aclockwise direction as indicated by the arrow R shown in FIG. 5.

Since flowport 181 exits fitting 183 through an exit opening 194off-center, as rotor 46 rotates concentrically, flowport 181 moves in aneccentric path. Connected to the lower end of fitting 183 by a threadedbolt 196 is a plate 198 through which extends an opening 200 which isalso off-center with respect to the centerline of plate 198. As seen inFIG. 5, opening 200 is in open communication with exit opening 194 fromflowport 181. Thus, as rotor 46 rotates, opening 200 also rotates in aneccentric pathway.

There is a second, annular plate 210 which is connected to a threadedfitting 212 received in a threaded female receptacle in sub 34. In thisregard, as seen in FIG. 5, plate 210 and fitting 212 have registeringbores, offset from the centerline, in which is press fitted a slottedtubular pin 214. Plate 210, as seen in FIGS. 5 and 7, has an offcenteropening 220, opening 220 being in open communication with a passageway222 which in turn is in open communication with a central fluidpassageway 224, passageway 224 defining an exit for fluid passingthrough pulsing apparatus 26 in a downhole direction.

As best seen in FIG. 6, opening 220 is generally crescent-shaped. Morespecifically opening 220 has a modified crescent shape comprised of agenerally semi-circular portion 230 which extends from about point A toabout point B, a straight portion 232 which extends from about point Cto about point D, a first arc portion 234 which extends between point Aand point C and a second arc portion 236 which extends between point Band point D. Opening 220 can also be described as bean-shaped,kidney-shaped, etc. As seen in FIG. 5, the passageway defining opening220 has a first, upper, vertical wall portion, the wall surface beinggenerally parallel to the long axis of the pulsing tool 26, and secondlower skirt portion 252 which, as seen in FIG. 5, flares outwardly fromthe intersection of skirt portion 252 with upper portion 250.

FIGS. 8 and 9 show a modified version of opening 220 as indicated by thesection lines (8)-(8). Turning then to FIGS. 8 and 9, it can be seenthat crescent-shaped opening 220A has a chamfered lip portion 254extending from the upper surface of plate 210A downwardly, chamfer 254extending for approximately a peripheral distance determined by points Aand C. In all other respects, as seen in FIG. 9, the passageway formingopening 220A is the same as described above with respect to opening 220.

As can be best seen by comparing FIGS. 5 and 6, at all times there issome overlap between fixed opening 220 and eccentrically rotatingopening 194. This ensures that at all times while the mud pumps areoperating, there is fluid flow through the drill string. It will also beappreciated that as rotor 46 rotates, the degree of overlap betweenopenings 220 and 194 will vary, resulting in flow changes and hencepressure pulses resulting in pulsing of mud passing through pulsingapparatus 26.

In operation, but prior to the mud pumps being turned on, there would ofcourse be no flow through pulsing apparatus 26. However, activation ofthe mud pumps forces drilling mud or fluid down the drill string. Whenthe pressure of the flowing mud reaches a predetermined pressure, valve40 opens, the degree of opening depending upon the pressure of the mudand the spring force of the spring 79. At the same time, and as can beseen from the above description, there is also flow through an annularpath defined primarily by the annuli formed by the rotors and stators.Thus, the above referenced central flow path, at least in part is formedby passageways 96 and 180.

The angles of the vanes in rotors/stators can vary to at least partiallycontrol the velocity of the mud through the annular flow path. Thus, allthe vanes of all the rotors/stators can be at the same angle or atslightly different angles. Likewise, flow through the central passagewaycommencing with valve 40 is controlled not only by mud pump pressure butalso by the spring force of spring 79 determined by the spring constant.

It will also be appreciated that the plug valve, i.e., valve 40 can beused to more readily control flow through the central passageway of thefirst stage to the second stage of the pulsing apparatus 26. In thisregard, the conical shape of valve plug 70 coupled with the valve inlet68 being formed by a frustoconical wall ensures greater throttlingcontrol of fluid flow through the central passageway. This is importantsince speed of rotation of the rotors in the pulsing apparatus 26 isprimarily a function of flow through the annular flowpaths. To controlrotation, and hence frequency of pulsing, that flow must be modulatedwhich is accomplished by valve 40.

Although the application has been described above with respect to atwo-stage pulsing apparatus, a stage being a stator and a rotor, it isto be understood that it is not so limited. The pulsing apparatus couldinclude only one stage, two stages as described, or more stages.Furthermore, it will be recognized that the stator vanes impart aspiraling flow path which ensures the fluid impinges on the rotor vanesat the optimum angle of attack.

It will be understood from the above description that flow exitingpulsing apparatus 26 is in the form of a series of pressure pulses.These pressure pulses are used to provide a percussive action along theaxis of the drill string 12. Furthermore, the fluctuations in thedrilling fluid flow rate at drill bit 20 provide for effective cleaningof cuttings from the drill bit during the drilling operation.

The pressure pulses may also be used, as is well known to those skilledin the art, to operate shock subs or to move a reciprocating mass whichimpacts on an anvil, with the aim of providing a percussive or hammeraction to a system drilling in hard rock. Shock subs useful with thepulsing apparatus of the present invention are well known to thoseskilled in the art.

In addition to its uses in drilling, the pulsing apparatus of thepresent invention can be used in such operations as: (a) reducingfriction in drilling operations; (b) shaking of tubing to clean screens;(c) vibrating of cement during cementing operations; (d) pulsating fluidbeing pumped into a formation to fracture it; (e) enhancing the fishingoperation through inducing impulse vibration to the drill string.

Although specific embodiments of the invention have been describedherein in some detail, this has been done solely for the purposes ofexplaining the various aspects of the invention, and is not intended tolimit the scope of the invention as defined in the claims which follow.Those skilled in the art will understand that the embodiment shown anddescribed is exemplary, and various other substitutions, alterations andmodifications, including but not limited to those design alternativesspecifically discussed herein, may be made in the practice of theinvention without departing from its scope.

What is claimed is:
 1. A downhole pulsing apparatus comprising: anelongate tubular housing having a first end and a second, there being anaxial fluid flow pathway through said housing; a first valve disposedproximal said first end of said housing to at least partially controlthe flow of fluid through said housing, said first valve having a valveinlet and a valve outlet; at least one vaned stator having a pluralityof circumferentially spaced, angled first vanes to direct fluid enteringsaid first end of said housing in a spiral pattern; at least one vanedrotor rotatably mounted in said housing below said at least one stator,said rotor having a central fluid passageway in fluid communication withthe outlet of said valve, said rotor having a plurality ofcircumferentially spaced, angled second vanes rotatable with said rotor,flow from said stator impinging on said rotor vanes resulting inrotation of said first rotor; a second valve mounted in said housing,said second valve having first and second valve members, each of saidvalve members having first and second axial flow openings, respectively,said first valve member being rotatable around a longitudinal axisthrough said housing, said second valve member being fixed, rotation ofsaid first valve member varying the alignment of said first and secondopenings between a minimum open area and a maximum open area to providea an intermittently varying flow and pressure exiting said second end ofsaid housing.
 2. The pulsing apparatus of claim 1, wherein said firstvalve member is operatively connected to said first rotor for rotationtherewith.
 3. The pulsing apparatus of claim 1, wherein there are aplurality of said rotors.
 4. The pulsing apparatus of claim 3, whereinthere are a plurality of stators, respective ones of said rotors beingpositioned below respective ones of said stators.
 5. The pulsingapparatus of claim 4, wherein said first valve member of said secondvalve is operatively connected to the rotor most proximal said secondend of said housing.
 6. The pulsing apparatus of claim 1, wherein saidfirst valve comprises an annular valve body, said annular valve bodydefining said valve inlet, and a valve element mounted in said valvehousing, said valve element comprising a valve plug connected to acompression spring, said valve plug substantially preventing fluid flowinto said valve inlet when said spring is in a relaxed position, fluidflowing through said housing acting on said valve plug to compress saidspring and increase the flow through said valve inlet.
 7. The pulsingapparatus of claim 6, wherein said valve plug is conically shaped. 8.The pulsing apparatus of claim 1, wherein said at least one rotorcomprises a first central core portion in surrounding relationship tosaid central passageway and a first outer sleeve, a first rotor annulusbeing formed between said first central core portion and said firstouter sleeve, said second vanes being disposed between andinterconnected to said first central core portion and said first outersleeve.
 9. The pulsing apparatus of claim 8, further comprising aplurality of angled ports in open communication with said centralpassageway and said first rotor annulus.
 10. The pulsing apparatus ofclaim 8, wherein said first central core portion of said at least onerotor is connected to a second rotor for rotation therewith, said secondrotor comprising a second central core portion and a second outersleeve, a second rotor annulus being formed between said second centralcore portion and said second outer sleeve, the vanes of said secondrotor being disposed in said second rotor annulus.
 11. The pulsingapparatus of claim 8, wherein said central core portion includes anaxially extending shaft portion and said second rotor has an axiallyextending bore for receipt of said shaft.
 12. The pulsing apparatus ofclaim 11, wherein said shaft is connected to said second central coreportion by a pin received in registering holes in said shaft and saidsecond central core portion.
 13. The pulsing apparatus of claim 6,wherein said valve body has a generally cylindrical portion and agenerally frustoconical portion, said frustoconical portion definingsaid valve inlet.
 14. The pulsing apparatus of claim 1, wherein saidsecond axial flow opening in said second valve member is generallycrescent-shaped when viewed in plan view.
 15. The pulsing apparatus ofclaim 14, wherein said generally crescent-shaped opening forms the mouthof a passageway extending through said second valve member, said secondvalve member comprising a disc-shaped plate having an upper surfaceproximal said first valve member, said passageway through said secondvalve member having a chamfered lip portion extending from said uppersurface into said passageway, said lip portion extending for a portionof the periphery of said crescent-shaped opening.
 16. The pulsingapparatus of claim 1, wherein said first valve member comprises a seconddisc shaped plate.